Process for rendering gelatin insoluble and its application to various arts



- so thickness be 4o tin and silver Apr. 16,, 1929.

UNITED STATES ATEN OFFICE.

amen m: raocounmn-eonsn Ann-moons SIGNOBS 'ro socniri: DE rno'roomum rnocnss ma n'nnnnnme enna'rrn IN'SOLUBLE ARTS.

ELKA, or men, Ii-men. AND ITS urnca'rron r venous Io Drawing. Application filed November 1 1, 1925, Serial No. 88,460, and in France November 18,1834.

roznmxow, or mcnraa mm, as-

This invention relates to renderinggelatin and until the solution again becomes cominsoluble and the application ant product to various arts. I According to this invention a pure gelatin 6 is intimately mixed with silver halid prepared separately and containing no trace of colloidal substances. The mam thus obtained possesses a'property such that, wherever the silver halid is subsequently reduced 10 by any known process, the gelatin is insoluble; such solubility being proportional of the resultto the quantity of the silver halid reduced.

Per contra, wherever the silver halid remains intact and pure and not reduced, the

gelatin remains soluble in water and may be eliminated by merely washing the mass with, for example, hot water.

One of the most important properties of the mass of gelatin and silver halid treated by reducing the silver and then washing,

will be set out hereinafter.

Suppose, for example, that there is present a layer of gelatin and silver halid, and that the silver halid emplo ed is in places more or less completely reamed (by exposure, for example, and then a treatment withsuitable developers), there is obtained, after washing with hot water, a layer whose thickness of gelatinwill also vary in places, such ing greatest wherever the reduc tion of the silver halid is complete and least wherever the*silver halid remains intact, and I 1 moreover, throughout proportional to the degree of redudtron of the silver halid.

Alayer is then obtained which will contain more or less marked reliefs which show the places where exposed silver halid has been more 'or less reduced.-

In order to pre are such mixture of gelafrom separately preparede'invention may be following example:

-'The two solutions following are prepared ure products. ustrated in the '45 separately:'-

i Solution A. Chemically pure silver nitrate 20 Distilled-'water'u-ul 200 9 After solution of the silver nitrate, am-

.monia' water is added in small doses until solution of the brown precipitate produced 1d, it is necessary to startcare mixed, filtered, and the emulsion pletely transparent.

' Solution B.

Pure photographic gelatin 1 grams.

Distilled water 203' grams. Chemically pure potassium bromide 18 grams.

, Absolute alcohol 30 cm.

This solution is heated to C. and then allowed to: cool to 30 C.

' he preparation of both these solutions maybe made in daylight.

Solution A is now heated to a temperature of 30 C. and is then added in small doses and with continuous agitation to solution B operating in a dark room with red light. e vessel containing a mixture thus obtainedis placed upon a water bath at 38 C. It is then covered-and allowed to cool as slowly as possible, every ten minutes;

The mixture is then placed ina centrifugal apparatus of any suitable type, which is then placed in movement; silver bromide is then 'obtainedand it is then only necessary to wash it with water.

40 grams of pure photographic gelatin are taken separately and thoroughly washed several times with very cold disti ed water.

After elimination of the excess water by the aid of bromide previously obtained, is added to the gelatin. 1

The gelatin and silver bromide are intimatel mixed together for the purpose of 'distri uting the possible throughout the mass. The vessel containing themis then placed in hot water thoroughly agitating- Pure ripened pressure, for example, the silver,

latter .as uniformly as is.

at atemperature of 45 C. and the mass is D fused while agitating carefully.

If the. entire mass seems to less brin it up to tliis measure.

of gelatin and'silver bromide is ready to be past-in any sh'apedesired, according to the .use for 'which'it is destined. It is preferable, moreover, not to cast at once, but to leave it in a cool place until use; it is then ;remelted at a 40 C. again filtered and cost.

temperature not exceeding I It will at once be seen to what numerous I applications the process may be put.

tion of the silver halid'has not been effected more or less strongly. The roof obtained is in its unfixed and unwas ed state then applied face downwards upon a clean and polished surface, such as glass, metal, celluloid, etc. (by the aid of an india rubber scraper, for example,)then placed in water having a temperature of 45 to 55 C. It will then be seen that wherever the gelatin has not been rendered insoluble, the emulsion runs beyond the edges of the paper and is dissolved in the water. By raising an edge of the paper, the latter can easily be removed, the image in relief remaining wholly upon the support, washing is continued until complete removal of the soluble emulsion. The image is then fixed in the usual manner for removing the silver halidretained in the insoluble gelatin. I

One may also, after developing, and after allowing the developer to drain off, rapidly plunge the unwashed proof in an ordinary 20% fixing agent, for example, which is replaced after two or three minutes by a fresh fixing agent. The paper is left for about 15 minutes in the bath, washed in running water, allowed to dry and the proof again placed in cold water and then applied upon a backing and then operating as above described. The image will adhere very strongly to the backing.

In this latter operating method, the unreduced silver is eliminated by the fixing and the insoluble gelatin and the reduced silver. remain in the sensitive layer, the soluble portion of the gelatin being removed by the hot water.

In both cases the image obtained presents a very considerable relief.

It may be remarked that the exposure of the sensitive layer is here almost instantaneous, contrary to that produced with sensitized layers, in which biehromates are employed to render the gelatin insoluble.

The sensitized layer obtained in accordance vwith the present invention permits. also of the making of enlargements.

ing, the image The image in relief, obtained as above described, and which is easily transferable from one support to another, may, in particular, be transferred upon a metal plate, in order to obtain engraved plates for printing, advertisement-s, etc. The plates thus obtained possess a remarkable fineness hitherto unobtainable. The fincness of the grain may be pushed to its maximum degree, and regularity of etching is perfect. This process is also applicable to rotary photoprinting, to zincography' and all other photo-mechanitail processes (even for polychrome reproductions. Generally .speakin relief may be transferred to any support in view of any subsequent treatment desired.

The transferred image in relief willretain its exact dimensions.

Bleached in the ordinary manner by potassium bichromate or potassium ferrieyanide, and then fixed, the proof may be coloured by saturation or by formation of insoluble lakes (colour photography).

Finally, in accordance with this invention, the gelatin rendered insoluble by this process may be employed for producing articles, low reliefs, etc. by direct photography from the mass of gelatin, the gelatin which has'remained insoluble being eliminated by washing.

In order to allow of the ready observation of the degree of the etching on a'sheet of metal when producing a printing plate, which is difficult to see because of the gelatin being rendered black by the presence of reduced silver, the sensitized layer may .be coloured by the addition, "at any period-of colouring matter.

The colouring matter may be one which does not produce any chemical action upon the silver halid and is readily assimilated by and distributed uniformly throughout the sensitized layer. It should also be transparent to the light of; the laboratory, in which the development of the sensitized layer is efieeted, in order to allow of its control.

It has been found that the best tint to give to the sensitized layer is a red tint, which may be obtained by the aid of any reg colouring matter, in particular, aniline re s. Y

Other colours may, however, be employed, in accordance with the use to which the sensitized layer is to be applied.

It has moreover been observed that a red coloration of the sensitized layer has for effect substantially to attenuate the action of the light on the sensitized layer, during its exposure, and thus to diminish the magnitude of the reliefs.

By tinting the sensitized layer in red, reliefs will be obtained which are less prominent andsoft, and, moreover, the bite process when makin easily followed.

Claims; 1. A process of preparing insoluble gelatin relief images which consists in preparing ripened silver halide substantially free from colloidal substances, mixing the silver halide with dissolved pure gelatin to form a li ht sensitive emulsion, exposing the emulslon variously at predeterminedpoints of its sur face, subjecting the emulsion to the action of a developer to reduce the exposed silver halide therein, and washing'o'ut the undeveloped portions of emulsion and halide.

2. A rocess of reparing insoluble gela-l 1 tin relie images w ich consists in preparing ripened silver halide substantially free from colloidal substances, mixing the pure ripened silver halide with pure gelatin to form a light sensitive emulsion, combining the emulsion with -a material ada ted to color the gelatin, exposing the'em s'ion variously at predetermined oints of its surface, subecting the emu veloper to reduce the exposed silver halide g printing plates is more sion to the action .of a de-s I therein, and washing out the undeveloped portions of emulsion and halide.

3. A process for the manufacture of photo'- graphic proofs, in relief, which consists in mixing pure gelatin with separately prepared ripened silver halide, placing the mix- .ture upon a backing, exposing to light, developing, transferring ulpon anothersupport and washing out the so uble gelatin.

4. process ofpreparing insoluble gelatin relief images which consists in combining thegelatin with ripened silver halide substantially free from colloidal substances, forming a body therefrom, exposing the said body at predetermined intensities at difi'erent parts 0 its surface, reducing the exposed silver halide to produce a local insolubiliza' tion of said 'ge atin, and washing out the soluble elatin emulsion and unexposed silver halic le.-

In testimony that we claim the foregoing as invention, we have signed our'names this 24th day of October, 1925.

SERGE DE PROCOUDINEI-GORSKY. NICOLAS PO 0w. a 

